Because many years typically elapse between etiologic carcinogenic exposures and the subsequent occurrence of cancer, epidemiologists often must use indirect estimates of historical exposures for study participants. Earlier work suggests that historical data on crops and associated pesticide applications can be used to estimate the probability of agricultural pesticide exposures among persons living near fields, but this retrospective work could not ascertain whether nearby residents actually were exposed. However, a prospective study that collects environmental and biological samples from households at different distances from agricultural fields would 1) reveal whether a clear exposure gradient occurs as a function of distance from the fields, and 2) indicate whether there is a correspondence between measured exposures and a records-based method for predicting household member pesticide exposures. If a predictable exposure gradient occurs with increasing distance from the fields, then retrospective exposure estimates could be further refined to account for this gradient. We propose to study the herbicide atrazine as a marker of pesticide exposure in persons living near corn fields in Illinois in areas with 1) pockets of rural housing located in proximity to cornfields, and 2) towns and communities that lie in juxtaposition to agricultural lands. To identify specific areas and specific houses, we will use a variety of data including: the U.S. Census of Agriculture and the Illinois Agricultural Statistics Service, aerial photography and/or satellite imagery, GIS data sets, localized census data (block, block group and census tract levels), and topographic maps. From each of the 50 households that we enroll, we will include one adult and one child younger than 4 years from whom we will obtain a urine sample; we will also obtain a house dust sample and drinking water sample from each home. A questionnaire will capture information about behaviors and housing characteristics that might influence the participants' pesticide dose. The proposed study will help reveal whether records-based techniques will be useful for reconstructing pesticide exposures and whether the use of additional exposure-related variables increases the precision of the exposure estimates.